Finding crayfish in North Delta’s Cougar Creek

Down in Lower Cougar Creek, the water flows lazily over a bottom of rocks and sand. Leaves gently drop onto the surface of the water, moving through dabbles of sunlight and the shadow of birch trees.

Sitting solemnly at the bottom, a red-shelled crustacean waits. Its many legs are motionless; its lobster-like tail lays flat behind it and is still. The only movement is a slight twitching in its antennae as the current drifts past.

It is a signal crayfish, Pacifastacs leniusculus: a freshwater crustacean native to parts of British Columbia and much of the Western United States.

Small (generally around 7.5 cm long, although they can be as little as 2.5 cm or as large as 40 cm) and nearly inconspicuous among the rocks, crayfish are commonly associated with the waters of Southeastern America: land of Cajun cooking and Bayou blues. Known also as crawfish, crawdads, mudbugs and freshwater lobsters, American crayfish have the richest biodiversity of all crayfish species.

Of the 500-odd crayfish species found globally, about 400 are found in North America. Nearly 70 per cent of those are found in the United States, the majority living in waters east of the Rocky Mountains.

In the Lower Mainland, “they’re around. They’re just not that common, so people tend to think its very unusual to see them,” said Eric Taylor, director and curator of fishes at the Beaty Biodiversity Museum and a professor in UBC’s department of zoology.

“It’s not really unusual, it’s just that people don’t normally look for them,” he added. “It’s not like watching a bird or something people can easily see, you kind of have to look for them.”

The crayfish sitting at the bottom of Cougar Creek, although coloured in red, brown and white, looked at first like a protrusion on the rock beneath it. Only after minutes of scanning the water did it reveal itself to be a living crustacean.

Another crayfish was hiding not too far away in the pebbled bottom of the creek. It was camouflaged until it began to move, picking its way through the rocky terrain.

Crayfish are bottom dwellers, eating woody debris, other crustaceans, algae and insects. Mating for many varieties of crayfish begins in October: the eggs attach themselves to the female’s abdomen until April or May, when they hatch and eventually learn to forage away from their mother.

Like any species, crayfish can become a destructive force when introduced to lakes and streams where they weren’t before. This may have been the case in certain Vancouver Island lakes, Taylor said, where signal crayfish were first found in the early 2000s.

“They tend to devastate small-bodied fishes that live on or near the bottom, because they rout around in their fish nests,” Taylor said. In Vancouver Island, introduced crayfish likely brought about the loss of several unique fish populations.

But in Cougar Creek, crayfish are happy and at home.

“The good thing about seeing crayfish is it shows you the general health of your stream,” Bob Scanlon, a member of the Cougar Creek Streamkeepers, said. “If you’re seeing crayfish, then your stream’s healthy.”

The two crayfish at the bottom of the creek continued their daily routine. The larger, red crustacean remained immobile on the rock, the smaller crayfish settled down between two pebbles for a rest.

Then, a third appeared. This one was faster than the others, scrambling over the bottom with its many-legged abdomen. It crawled over rocks, between rocks, around rocks. Then, it stopped. Birds screeched in the distance.

If you looked away, perhaps to see where the noise was coming from, the crayfish would be gone, seemingly melted into the stream floor. But although you can’t see it, the crayfish is there — silent among the rocks.